Flow-turning device and method for producing internally geared wheels using two sets of internal toothing

ABSTRACT

The invention relates to a flowturning device ( 1; 101 ) for producing an internal geared wheel (17) with inner toothing, one set of which is slanted. The workpiece ( 9 ) is held by a retaining member ( 16; 116 ) during shaping of the first inner toothing. The workpiece ( 9 ) is held by the first toothing on the first shaping toot ( 2; 102 ) during shaping of the second inner toothing. Once the internal geared wheel ( 17 ) has been finished, the rotational coupling between both shaping tools ( 2, 4; 102, 104 ) is detached. The internal geared wheel ( 17 ) is detached from the slanted toothing(s) by means of a stripping member ( 18 ).

BACKGROUND OF THE INVENTION

The invention relates to a flow-turning device and to a method forproducing internally geared wheels using two sets of internal toothingarranged axially one behind the other, at least one of which is ahelical toothing. By helical toothing is also to be understood a screwthread.

Internally geared wheels having sets of internal toothing that are madeof steel alloys and other metallic materials are used in particular forpower transmission in driven wheels of heavy goods vehicles or tractors,for example. Internally geared wheels of this type have at their forwardends sets of internal toothing that are accessible from the outside. Thetwo sets of internal toothing can have a different diameter if theinternally geared wheel is to be used in a gearbox, for example. Theinternally geared wheel can have a spur toothing, in which the teethextend parallel to the axis of rotation, or a helical toothing or screwthread.

WO 96/20050 describes a method for producing internal geared portions,in which method internally geared wheels having two sets of internaltoothing are produced as a result of pressure rollers flow-turning theworkpiece over shaping tools. In this connection, however, onlyinternally geared wheels having spur toothing on both sides can beproduced.

SUMMARY OF THE INVENTION

The underlying object of the invention is to improve the production ofinternal geared portions to the extent that even portions having twosets of internal toothing, at least one of which is a helical toothing,are simple to produce.

This object is achieved in accordance with the invention by means of thefeatures of claims 1 and 8.

The invention proposes a flow-turning device which has a first and asecond shaping tool each having an external toothing, pressure rollersfor flow-turning a workpiece sitting on the shaping tools which areconnected to each other, and holding means which secure the workpieceagainst rotation during the flow-turning of the first internal toothingon the first shaping tool. At least one of the shaping tools has ahelical toothing, in which the individual teeth extend in the manner ofa screw thread at an angle to the longitudinal axis of the shaping tool.There is provided at least one stripping element, which pushes thecompleted internally geared wheel off of the shaping tool or tools withhelical toothing with relative rotation between shaping tool andinternally geared wheel. During the production of the internally gearedwheel, the two shaping tools are coupled to each other in a rotationallysecure manner. After the production, this rotationally secure couplingis lifted, so that one shaping tool rotates together with the internallygeared wheel while the internally geared wheel is detached from theother shaping tool with the aid of the stripping element. As a result ofthis, one-piece internally geared wheels having two sets of internaltoothing, at least one of which is a helical toothing, can be producedin one operation, i.e. without having to rechuck the workpiece.

The holding means can be a movable sleeve surrounding the second shapingtool. The sleeve presses the workpiece against the first shaping toolwhile the first internal toothing is formed. In this connection, thesleeve holds the workpiece on the shaping tools and simultaneouslysecures it against rotation. After this, the sleeve is pulled back inorder to be able to form the second internal toothing. The workpiece isthen held firmly on the shaping tool by the first toothing.

The holding means can also be a stamped element of the first shapingtool, such as an end toothing, for example. At the start of the forming,the workpiece is pressed by the contact force of the pressure rollers onto this end toothing, so that a rotation of the workpiece is preventedwithout further holding means.

In a preferred embodiment of the invention, one of the shaping toolsprotrudes from a tool holder which is movably guided in the othershaping tool and can act upon the latter for rotational entrainment. Thetwo shaping tools are therefore freely accessible from one side, so thatthe workpiece can easily be slid on to the two shaping tools and thecompleted internally geared wheel can easily be pushed off from the twoshaping tools. Thus, it is also possible to produce internally gearedwheels which have, behind a toothing, a shoulder which has a smallerdiameter than the toothing, for the internally geared wheel is strippedfrom the shaping tools. The shaping tool does not have to be pulled outthrough the shoulder which has a comparatively small diameter.

In a further embodiment, the end of the second shaping tool that facesthe first shaping tool has a smaller diameter than the external toothingof the second shaping tool. This renders possible a simpleconstructional design of the flow-turning device, for the second shapingtool is easily enclosed in an end-face bore of the first shaping tooland, after the internally geared wheel has been completed, can alsoeasily be pulled out both from the first shaping tool and from theinternally geared wheel, because the end of the shaping tool, because ofits comparatively small diameter, can be moved through the internaltoothing.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplifying embodiments of the invention are explained with the aid ofthe drawings, in which:

FIG. 1 shows a first exemplifying embodiment during the forming of thefirst toothing;

FIG. 2 shows the first exemplifying embodiment during the forming of thesecond toothing;

FIG. 3 shows the stripping of the internally geared wheel; and

FIG. 4 shows a second exemplifying embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In the exemplifying embodiment of FIGS. 1 to 3, the flow-turning device1 has a first shaping tool 2 in the form of a hollow mandrel. This isrotatably fastened on the shaft of a machine. The machine is not shownin the Figures; it is located on the left next to the flow-turningdevice 1. On the end facing away from the machine, the shaping tool 2has a helical toothing 3.

A second shaping tool 4 extends in the central hollow space of the firstshaping tool 2 and protrudes from an end-face opening of the firstshaping tool 2. It is fastened to a shaft-side tool holder 5 which islocated in the central hollow space and can be rotated and moved in theaxial direction by the machine. A conical surface 7 of the movable toolholder 5 engages in a corresponding inner cone of the first shaping tool2 for rotational entrainment. In order to generate a conical clampingbetween the tool holder 5 and the first shaping tool 2, a hollow mandrel8 actuated by the machine is pressed against the first shaping tool 2.The second shaping tool 4 has on its protruding end a parallel toothing6 which has a smaller diameter than the helical toothing 3. The twoshaping tools 2, 4 consist of chromium-containing ormolybdenum-containing materials which are coated and surface-hardened.

In accordance with FIG. 1, the workpiece 9 which is to be formed inorder to form an internally geared wheel is already preformed in such away that in each case there is a short tubular circumferential region 9a or 9 b over the start of the sets of toothing 3 and 6 respectively.These tubular regions 9 a, 9 b have a greater wall thickness than theinternally geared wheel to be produced, because the tubular regions 9 a,9 b are flow-turned to a greater length and smaller wall thickness. Theradial region 9 c of the workpiece 9 that connects the two tubularregions 9 a, 9 b, on the other hand, already has the desired wallthickness because it is not subjected to deformation.

Pressure rollers 10 made of hard metal or HSS steel form the workpiece 9on to the shaping tools 2, 4. The pressure rollers 10 are arranged in aradial plane and rotate about their centre axis 11 with simultaneousforward feed. The pressure rollers 10 are pressed with a radial forceagainst the workpiece 9. The pressure applied in this way can amount to≧35 t, for example. In order that the pressure rollers 10 process evenlythe complete circumference of the workpiece 9, a rotatory relativemovement between the workpiece 9 and the pressure rollers 10 has to takeplace. In order to do this, either the shaping tools 2, 4 can be rotatedwith the workpiece 9 held securely thereon, or the pressure rollers 10can be moved circumferentially around the workpiece 9.

A tailstock-side mandrel 12 of the machine has a spring assembly 13arranged around a centring pin 12 a of the tailstock-side mandrel 12.The centring pin 12 [sic] engages in an end-face centring opening 14 ofthe second shaping tool 4. The mandrel 12 is movable in the axialdirection. This construction forms an ejector 15, which can release thetool holder 5 from the conical clamping with the first shaping tool 2.The tailstock-side mandrel 12 and also the toothing 6 of the secondshaping tool 4 are surrounded by a movable holding sleeve 16, whichholds the workpiece 9 on the shaping tools 2, 4 in a rotationally securemanner.

At the start of the flow-turning operation, the workpiece 9 is pushedfrom the tailstock side on to the two shaping tools 2, 4, in which casethe ejector 15 and the holding sleeve 16 are pulled back, i.e. separatedfrom the second shaping tool 4. In order to secure the workpiece 9, theholding sleeve 16 is then moved forwards. It presses the workpiece 9against the end face of the first shaping tool 2. The machine-sidehollow mandrel 8 is moved forwards until the spring assembly 13 restsagainst the tailstock-side mandrel 12, which is moved into position,when in the compressed state. The effect of this is that the tool holder5 enters into a conical clamping with the first shaping tool 2,something which leads to a rotationally secure coupling of the twoshaping tools 2 and 4. Simultaneously, the spring assembly 13 of theejector 15 is placed under pressure. The first shaping tool 2, the toolholder 5 with the second shaping tool 4, the hollow mandrel 8, theejector 15 and the holding sleeve 16 therefore form together with theworkpiece 9 a rotating unit.

The pressure rollers 10 are now brought up to the tubular region 9 a ofthe workpiece 9 that surrounds the start of the helical toothing 3 ofthe first shaping tool. In this connection, each pressure roller 10rotates about its axis 11. The pressure rollers 10 are moved jointlytowards the machine, in which case they push the material of theworkpiece 9 before them and simultaneously press it into the helicaltoothing 3 of the first shaping tool 2, so that an internal toothing isproduced in the workpiece 9. A pressure roller 10 a in the end positionand also the completed first internal toothing of the workpiece 9 areshown at the bottom of FIG. 1.

FIGS. 1 and 2 each show two processing steps. In each case, the pressureroller 10 and the workpiece 9 are shown at the start of the forming inthe upper half of the Figures and at the end of the forming in the lowerhalf of each Figure.

FIG. 2 shows how the second internal toothing is formed. After the firsttoothing has been completed, the holding sleeve 16 is drawn back,because the workpiece 9 is now held by the first helical toothing. Whilethe first toothing is produced in the same-direction pressing method, inwhich the forward-feed direction of the pressure rollers 10 correspondsto the material-flow direction, the second toothing is produced in theopposite-direction pressing method. In this connection, the materialflows in the opposite direction to the forward-feed direction of thepressure rollers 10. Starting from a starting position 10 b of thepressure rollers 10, the latter are moved towards the first shaping tool2. In this connection, the material which becomes soft in places underthe pressure roller 10 is pressed into the contours of the paralleltoothing 6 and thereby pressed in the direction of the tailstock, sothat the internal thread of the workpiece 9 is formed completely oncethe pressure rollers 10 have reached the end position 10 c.

The manner in which the completed internally geared wheel 17 is removedfrom the flow-turning device 1 is now explained with the aid of FIG. 3.After the pressure rollers 10 have been moved away from the internallygeared wheel 17, the machine-side hollow mandrel 8 is moved back, sothat the spring assembly 13 pushes the tool carrier 5 with the secondshaping tool 4, which has the parallel toothing 6, out of the conicalclamping in the first shaping tool 2. Because of the parallel toothing 6of the second shaping tool 4, the latter can be moved in the internallygeared wheel 17. If the second toothing 6 is a helical toothing, thedetachable rotational coupling between the first shaping tool 2 and thesecond shaping tool 4 is realised in another way, because the secondshaping tool 4 would no longer be able to be shifted in the axialdirection in the internally geared wheel 17. The rotational couplingcan, for example, be realised with detent pawls which engage in theother shaping tool and are pulled back again after the internally gearedwheel 17 has been completed.

After the rotational coupling between the two shaping tools 2, 4 hasbeen removed, a stripping sleeve 18, which surrounds the first shapingtool 2, is pressed against the end face of the internally geared wheel17. The stripping sleeve 18 has, on its end face which presses againstthe internally geared wheel 17, an axial bearing 19, so thattranslational, but not rotational, movements can be transmitted. Inorder to release the internally geared wheel 17, the stripping sleeve 18is pressed against the end face of the internally geared wheel 17, sothat the latter is pushed in a rotating manner away from the firstshaping tool 2. At the same time, the internally geared wheel 17 slidesin the direction of the tailstock and is thus pushed in a rotatingmanner away from the shaping tool 42 [sic]. The released internallygeared wheel 17′ (here shown with dashed lines) can be removed from theflow-turning device 1 as soon as the ejector 15 is moved to thetailstock side and thus separated from the second shaping tool 4.

If the second toothing 6 is also a helical toothing, there is provided asecond stripping sleeve which extends on the ejector 15, in order to beable to detach the internally geared wheel 17 from the second toothingas well in the same way.

FIG. 4 shows a second exemplifying embodiment of the flow-turning device101. The first shaping tool 102 likewise has a helical toothing 3. Itis, however, not constructed as a hollow mandrel, but instead is tubularwith an end-face central opening in which the second shaping tool 104engages. The second shaping tool 104 has a parallel toothing 6 and issecurely connected to the tailstock-side tool mandrel 12.

In order to place the workpiece in the flow-turning device 101, first ofall the tailstock-side tool mandrel with the second shaping tool 104 ispulled out of the first shaping tool 102 and the workpiece is positionedon the first shaping tool 102 and then the second shaping tool 104 ispushed through the workpiece into the opening of the first shaping tool102. A rotationally secure coupling of the two shaping tools 102, 104can take place by pressing together the two shaping tools 102, 104 or,for example, by detent pawls (not shown). Then, as described above, thefirst internal toothing is formed. A holding sleeve is not absolutelynecessary, because the first shaping tool 102 has an end-face toothing116, against which the workpiece is pressed by the pressure rollers atthe start of the shaping process, so that the workpiece and the firstshaping tool 102 enter into a rotationally secure connection.Additionally, however, a holding sleeve can still be provided. Thesecond internal toothing is also formed as described above. After theinternally geared wheel 17 has been completed, the rotational couplingbetween the two shaping tools 102, 104 is released, the stripping sleeve18 is pressed against the internally geared wheel 17 and the firstshaping tool 102 is rotated out of the internal toothing of theinternally geared wheel 17. The tailstock-side tool mandrel 12 is pulledout of the internally geared wheel 17, so that the latter can be removedfrom the flow-turning device 101.

What is claimed is:
 1. Flow-turning device (1; 101) for producing aninternally geared wheel (17) having two sets of internal toothing, saidflow-turning device having a first (2; 102) and a second (4; 104)shaping tool each having an external toothing (3, 6), in which devicethe two shaping tools (2, 4; 102, 104) can be coupled to each other in arotationally secure manner for flow-turning, the flow-turning devicehaving pressure rollers (10) for flow-turning a workpiece (9) sitting onthe shaping tools (2, 4; 102, 104) which are connected to each other,and having holding means (16; 116) which secure the workpiece (9)against rotation during the flow-turning of the first internal toothingon the first shaping tool (2; 102), characterised in that at least oneshaping tool (2; 102) has a helical toothing (3), and in that there isprovided at least one stripping element (18) which is movable in thelongitudinal direction and which, after the mutual coupling of the twoshaping tools (2, 4; 102, 104) has been released, pushes the completedinternally geared wheel (17) off of one shaping tool (2; 102) withhelical toothing (3) with relative rotation between shaping tool (2;102) and internally geared wheel (17).
 2. Flow-turning device accordingto claim 1, characterised in that the holding means is a sleeve (16)surrounding the second shaping tool (4; 104).
 3. Flow-turning deviceaccording to claim 1, characterised in that the holding means is astamped element (116) of the first shaping tool (102).
 4. Flow-turningdevice according to claim 1, characterised in that the stripping element(18) is a sleeve which is movable on a shaping tool (2; 102) and can bepressed with an axial bearing (19) against the internally geared wheel(17).
 5. Flow-turning device according to claim 1, characterised in thatthe one shaping tool (4) protrudes from a tool holder (5) which ismovably guided in the other shaping tool (2) and acts on the latter forrotational entrainment.
 6. Flow-turning device according to claim 5,characterised in that an ejector (15) for releasing the rotationalentrainment after the end of production acts on the free end of the oneshaping tool (4).
 7. Flow-turning device according to claim 5,characterised in that the end of the second shaping tool (104) that iscoupled with the first shaping tool (102) has a smaller diameter thanthe outside toothing (6) of the second shaping tool (104), so that thesecond shaping tool (104) can be pulled out of the internally gearedwheel (17).
 8. Method for producing internally geared wheels (17) havingtwo sets of internal toothing, at least one of which is a helicaltoothing, using a device (1; 101) which has a first (2; 102) and asecond (4; 104) shaping tool each having an external toothing (3, 6) andpressure rollers (10) for flow-turning a workpiece (9) on the sets ofexternal toothing (3, 6) of the shaping tools (2; 102, 4; 104), themethod having the following steps: placing the workpiece (9) on theshaping tools (2; 102, 4; 104), securely coupling of the two shapingtools (2; 102, 4; 104) against rotation, activating at least one holdingmeans (16; 116) for rotationally securing the workpiece (9) during theflow-turning of the first internal toothing on the first shaping tool(2; 102), flow-turning on the first shaping tool (2; 102), flow-turningon the second shaping tool (4; 104) releasing the rotational securingbetween the two shaping tools (2, 4; 102, 104), pushing the internallygeared wheel (17) from one shaping tool (2; 102) with a strippingelement (18), and separating the internally geared wheel (17) from theother shaping tool (4; 104).